Motorcycle muffler is an indispensable part in the development history of motorcycle, and the development history of motorcycle muffler is as long as that of motorcycle. After the engine has done its work, it is followed by the exhaust stroke. Exhaust is to exhaust the exhaust gas in the cylinder. Because the exhaust gas at this time is high temperature and high pressure, it will be very noisy if it is discharged directly from the exhaust pipe. The function of muffler is simply to say that the air flow discharged by the engine passes through the porous pipe and partition board in the muffler, and then the noise is gradually attenuated, so as to achieve the purpose of noise reduction.
Working principle
1. Intake: at this time, the intake valve opens, the piston moves downward, and the mixture of gasoline and air is drawn into the cylinder
2. Compression: at this time, the intake valve and exhaust valve are closed at the same time, the piston moves upward, and the mixture is compressed.
3. Combustion: when the mixture is compressed to the minimum, the spark plug will ignite the mixture, and the pressure generated by combustion will push the piston downward and drive the crankshaft to rotate.
4. Exhaust: when the piston goes down to the lowest point, the exhaust valve opens, exhaust gas is discharged, and the piston continues to go up to discharge the excess exhaust gas.
Classification by principle
1. Dissipative muffler: this kind of muffler uses the sound absorption function of sound-absorbing material or structure to make the noise propagated along the pipeline attenuate with distance, so as to achieve the purpose of noise reduction. Commonly used sound-absorbing materials include fiberglass, low carbon steel wire mesh, felt, etc. This kind of muffler has good noise elimination effect on high frequency noise, but low frequency noise elimination performance is poor. In addition, because the sound-absorbing material is easy to be melted by the high-temperature exhaust gas discharged from the engine, the service life is short, and it is easy to be blocked by carbon deposits, oil sludge and so on to reduce or lose the sound attenuation effect, so the motorcycle seldom uses a single resistance muffler.
2. Resistance Muffler: this muffler is to make the sound wave of some frequency propagated along the pipeline reflect back to the direction of sound source at the sudden change by means of the sudden expansion (or contraction) of the pipeline section or the side connected resonance cavity, so as to achieve the purpose of noise elimination. It is more suitable to eliminate low and medium frequency noise, but it has a poor effect on high frequency noise.
Classification by structural type
1. Tube muffler: this kind of muffler is generally a resistance or impedance composite muffler, which is mostly used on motorcycles with medium and large displacement. The tube muffler is generally composed of exhaust pipe, connecting screw sleeve, muffler tube and tube core. An oil immersed asbestos sealing ring is arranged in the connecting screw sleeve to prevent air leakage at the interface between the exhaust pipe and the silencing cylinder. There are several diaphragms welded in the anechoic cylinder. The anechoic cylinder is divided into several anechoic chambers (n expansion chambers and 1 resonance chamber). There are inverted triangle guide grooves and many small holes on the cylinder core. When the high-temperature exhaust gas of the engine enters the muffler at high speed through the exhaust pipe, because the cross-section volume of the anechoic cylinder increases gradually, the air flow expands, the flow velocity decreases, and the strong impulse noise decreases. When the air flow continues to flow through the expansion chambers, due to the barrier, the air flow can only pass through the orifices and cylinder cores on the barrier, so the air flow is suddenly compressed, divided into many small flows, and then suddenly expanded, so many sudden changes, which plays a role in reducing exhaust noise.
2. Box muffler: Generally speaking, because the installation space of mopeds, especially seat type vehicles is relatively small, box muffler is mostly used, which is composed of shell, sound-absorbing filler, silencing pipe, etc.
Muffler material
According to the materials, the refitted muffler pipes can be divided into aluminum alloy motorcycle exhaust pipe, stainless steel motorcycle exhaust pipe, carbon fiber motorcycle exhaust pipe, titanium alloy motorcycle exhaust pipe and so on. Aluminum alloy tubes are lighter in weight, more colorful and cheaper in price, but the surface of the tubes is easy to wear, not as durable as stainless steel tubes. Stainless steel pipes are heavier and less colorful, but they are more durable and sound heavier than aluminum alloy pipes, so friends who play with refitting usually like to choose stainless steel pipes. However, the high price of the material itself cannot make it really highly popular. Carbon fiber tube weight is relatively light, generally are mainly black carbon fiber, durability is not comparable to stainless steel.
Modification of muffler
If the exhaust pipe can't exhaust the burned exhaust gas quickly, then the next intake stroke will not be able to absorb the fresh air quickly and completely; especially the waste exhaust left in the combustion chamber at the moment will affect the next combustion efficiency, so the horsepower performance will not be ideal naturally, which is why the exhaust pipe should be modified.
For one thing, the modification of exhaust pipe mostly starts from the middle and tail section, and the common methods are to thicken the pipe diameter, reduce the muffler, etc. Catalyst is also an important component in the modification of the exhaust pipe in the middle section. Although the basic function of catalyst is to purify the exhaust gas, it also has the function of eliminating resonance and transmitting it to the cockpit. The catalyst composed of many kinds of precious metals, according to the view of refitting, is indeed a major culprit hindering the smooth exhaust, and it is also a annoying hot spot, so many people will choose to replace it, often just a small part of the straight through, they can feel the smooth exhaust, and the sound will not be stuffy inside.
Regular maintenance of muffler
Because the engine is working, the fuel is not completely burned. In addition, there are some impurities in the fuel, so when the high-temperature exhaust gas from the engine passes through the exhaust muffler, there will be carbon deposits on the cylinder core and partition of the muffler. Over time, the accumulated carbon deposits will block the air flow channel, increase the exhaust resistance, reduce the noise reduction performance, and make the engine weak, which will affect the normal driving of the vehicle. If it is serious, it will cause the exhaust pipe to turn blue